This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Formation of Nano Structured Materials”.
1. What does the post treatment method involve in template synthesis procedure of NSM production?
a) Mixing precursors of NPs with the micelles
b) Introducing semiconductors into mesoporous materials
c) Grafting the NPs onto the pore surface of mesoporous material
d) Heat treatment of the mesoporous materials
View Answer
Explanation: Template synthesis method uses templates such as anodized aluminium oxide (AAO) and mesoporous materials for fabricating nanoparticles. This method uses two processes to impregnate the pores with NPs: insitu and post treatment. The post treatment process involves direct grafting of the NPs onto the pore surfaces of a mesoporous material. There are ways to carry out the post treatment operations including surface grafting via sorption, phase transitions, covalent grafting and so on.
2. Identify a property from the given options that is not found in microemulsions.
a) Isotropic liquid dispersion
b) Thermodynamically stable
c) Supersaturated solution
d) Optical clear dispersion
View Answer
Explanation: Microemulsions are optically clear, thermodynamically stable isotropic dispersion of immiscible liquids such as oil, water, and surfactant, frequently combined with a co-surfactant. The surfactant helps in stabilizing the nano-sized domain of one or both liquids.
3. Top down methods increase the number of coherent crystalline domains, with the decrease in the size of materials.
a) True
b) False
View Answer
Explanation: The top-down approach synthesizes NSMs by the progressive disintegration of a massive crystal. This generates individual nanometer size coherent crystalline domains that remain separated from each other. Hence, these methods increase the number of coherent crystalline domains with the continuing size reduction.
4. Which is the best method developed for controlling the size and morphology of NSMs?
a) Hydrothermal synthesis
b) Template synthesis
c) Sono-chemical method
d) Thermal decomposition
View Answer
Explanation: Thermal decomposition is considered to be the best method developed for producing NSMs whose size and morphology could be easily controlled. The process is usually carried out using compounds such as hydroxides, carbonyls, formates, nitrates etc of metals.
5. Identify a process not used for isolating the nanostructured materials (NSMs).
a) Decomposition of precursors
b) Precipitation from solutions
c) Inert gas condensation
d) Chemical vapour deposition
View Answer
Explanation: There are certain processes used to isolate the NSMs. These are inert gas condensation, precipitation from solutions and decomposition of the precursors. These methods result in isolated, ultrafine crystallites having uncontaminated surfaces.
6. How can the size of nanocrystals be altered in electrochemical synthesis of NSMs?
a) Altering pressure
b) Varying the reaction time
c) Keeping the temperature constant
d) Introducing catalysts
View Answer
Explanation: The electrochemical synthesis of metal nanocrystals relies on the reaction time, temperature, current density, distance between the electrodes and polarity of the solvents. Upon altering these factors the size of the nanocrystals could be tuned successfully.
7. Who coined the term microemulsions?
a) T.P.Hoar
b) William Ramsay
c) Ahmed Zewail
d) Rosalind Franklin
View Answer
Explanation: The term microemulsion was first used by professors at Cambridge University T.P.Hoar and J.H.Shulman, in 1943. The dispersion of immiscible liquids goes by few other names such as transparent emulsion, micellar solution, swollen micelle and solubilized oil.
8. Which method of NSM synthesis is a two stage process involving nucleation and crystal growth?
a) Microemulsion
b) Thermal Decomposition
c) Precipitation
d) Solvothermal method
View Answer
Explanation: Precipitation is a two-stage process involving the formation of nuclei followed by their growth into the precipitate particles that are eventually obtained. This method applies solution chemistry in order to prepare the precursor, which is then converted into the NSMs by chemical reactions.
9. How can defects be introduced in perfect crystals to form a new class of NSMs?
a) By depositing different molecules simultaneously
b) By subjecting the material to high energy by extrusion or shear
c) By consolidating the materials at room temperature
d) By precipitation from unstable states of condensed matter
View Answer
Explanation: Introduction of defects such as dislocations and grain boundaries in a perfect crystal can form a new class of NSMs. These disorders in the lattice can be brought about by subjecting the materials to high energy like extrusion, shear and energy irradiation.
10. Choose the correct statement from the following with respect to precipitation.
a) Crystal growth is the first stage of precipitation followed by nucleation
b) Growth of particles decreases with increasing supersaturation
c) Very feasible and easy method for controlling the particle size and distribution
d) Increase in the number of imperfections in the crystals with higher growth rate.
View Answer
Explanation: The precipitation method can be considered as a two-stage process – nucleation followed by crystal growth. The rate of growth of NPs increases with increasing super saturation. This inturn raises the number of imperfections in the resulting crystals. Moreover, difficulty arises in controlling the particle size and distribution.
Sanfoundry Global Education & Learning Series – Nanotechnology.
To practice all areas of Nanotechnology, here is complete set of 1000+ Multiple Choice Questions and Answers.
If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]
